Krzysztof Drabent

X-ray Crystal Structures, Electron Paramagnetic Resonance, and Magnetic Studies on Strongly Antiferromagnetically Coupled Mixed μ-Hydroxide-μ-N1,N2-Triazole-Bridged One Dimensional Linear Chain Copper(II) Complexes

Four new metal-organic polymeric complexes, {[Cu(mu-OH)(mu-ClPhtrz)][(H 2O)(BF 4)]} n ( 1), {[Cu(mu-OH)(mu-BrPhtrz)][(H 2O)(BF 4)]} n ( 2), {[Cu(mu-OH)(mu-ClPhtrz)(H 2O)](NO 3)} n ( 3), and {[Cu(mu-OH)(mu-BrPhtrz)(H 2O)](NO 3)} n ( 4) (ClPhtrz = N-[( E)-(4-chlorophenyl)methylidene]-4 H-1,2,4-triazol-4-amine; BrPhtrz = N-[( E)-(4-bromophenyl)methylidene]-4 H-1,2,4-triazol-4-amine), were synthesized in a reaction of substituted 1,2,4-triazole and various copper(II) salts in water/acetonitrile solutions. The structures of 1- 4 were characterized by single-crystal X-ray diffraction analysis. The Cu(II) ions are linked both by single N (1), N (2)-1,2,4-triazole and hydroxide bridges yielding one dimensional (1D) linear chain polymers. The tetragonally distorted octahedral geometry of copper atoms is completed alternately by two water and two BF 4 (-) anion molecules in 1 and 2 but solely by two water molecules in 3 and 4. Magnetic properties of all complexes were studied by variable temperature magnetic susceptibility measurements. The Cu(II) ions are strongly antiferromagnetically coupled with J = -419(1) cm (-1) ( 1), -412(2) cm (-1) ( 2), -391(3) cm (-1) ( 3), and -608(2) cm (-1) ( 4) (based on the Hamiltonian H = - J[ summation operator S i . S i+ 1]). The nature and the magnitude of the antiferromagnetic exchange were discussed on the basis of complementarity/countercomplementarity of the two competing bridges.

Stable hemiaminals containing a triazole ring

Reactions between 4-amino-1,2,4-triazole and nitro-substituted benzaldehydes in acetonitrile under neutral conditions afford stable hemiaminals, seven of which have been structurally and spectroscopically characterized. Two Schiff bases have also been obtained after the addition of hydrochloric acid to the reaction mixture. We describe a correlation between the conformation and configuration of the hemiaminals, and conclude that the formation of these species is determined by the substituents on the phenyl ring, as well as by the presence of 4-amino-1,2,4-triazole.

ESR studies of low-spin [N1,N4-bis(salicylidene)-S-alkyl-isothiosemicarbazonato]cobalt(II) complexes doped into the lattices of corresponding zinc(II) chelates

Abstract Direct template reaction of salicylaldehyde S-alkyl-isothiosemicarbazone with salicylaldehyde and its derivatives, in the presence of cobalt(II) [or zinc(II)] acetate, triethylamine and triethyl orthoformate yields the aqua-adducts of the corresponding N 1 ,N 4 -bis(salicylidene)-S-alkyl-isothiosemicarbazone complexes. ESR measurements of cobalt doped zinc complexes were performed. The spectra are typical for the z 2 > 1 ground state. The energies of the two excited doublet states were estimated on the basis of spin Hamiltonian parameters. A six-coordinate structure with coordination of the phenolic oxygen of an adjacent molecule has been proposed for the CoL·H 2 O complexes. The formation of low-spin pyridine adducts of the title complexes in the solid was shown.

Counter anion dependent symmetry ofCuII–4-amino-1,2,4-triazole polymeric chains

The symmetry changes and length of the symmetry independent part of [Cu(amtrz)3]n2+ (amtrz = 4-amino-1,2,4-triazole) polymeric chains driven by different anions in crystals with BF4− (1), BF4−/SiF62− (2) and SiF62− (3) have been studied by single crystal X-ray method.

Mössbauer study of Fe/III/-reducing sugar complexes

Iron/III/ complexes with glucose, galactose, mannose and lactose have been prepared. The Mössbauer and magnetic susceptibility data demonstrate the polymeric structure of the complexes. The thermal behaviour of the Fe/III/-glucose complex has been monitored by Mössbauer spectroscopy.

Mössbauer, magnetic and thermogravimetric studies of adriamycin ferric complexes

Abstract The 1:1, 2:1 and 3:1 Fe 3+ :adriamycin lyophylized mixtures have been investigated by means of Mossbauer, magnetic and thermogravimetric methods. The Fe 3 Ad complex, in which most likely one ferric ion coordinates to amino sugar and two others are chelated by four oxygens of the adriamycinone ring system, seems to be the major species formed in the studied samples of quelamycin.

Molecular conformation versus C–H⋯Ph weak hydrogen bonds in 4-(4-H-1,2,4-triazol-4-yl)-2-X-phenylmethanimine (X=CH3,Cl,Br) crystals

Abstract Three 4-(4-H-1,2,4-triazol-4-yl)-2-X-phenylmethanimines where X=CH3 (1), Cl (2), and Br (3) have been synthesised and characterised by spectroscopic, theoretical, and single crystal X-ray methods. Crystallographic analysis showed that conformation of 1 is non-planar whereas of 2 and 3 are planar. In the studied crystals the C–H groups in triazole residues participate in the C–H⋯N hydrogen bonds and additionally in the C–H⋯O (water) hydrogen bond in 2. The aromatic phenyl ring is an acceptor of two intermolecular C–H⋯Ph hydrogen bonds only in 1. Observed non-planar conformation of 1 and results of optimisation of molecular geometry by DFT method suggest that conformation of 1 is highly influenced by very week the C–H⋯Ph hydrogen bonds in studied crystals.

Synthesis and characterization of hybrid materials containing iron oxide for removal of sulfides from water

Hybrid materials containing iron oxides based on macroporous and gel-type sulfonic and carboxylic cation exchangers as supporting materials were obtained. Multiple factors, including the kind of functional groups, ion exchange capacity, and polymer matrix type (chemical constitution and porous structure), affected the amount of iron oxides introduced into their matrix (7.8-35.2% Fe). Products containing the highest iron content were obtained using carboxylic cation exchangers, with their inorganic deposit being mostly a mixture of iron(III) oxides, including maghemite. Obtained hybrid polymers were used for removal of sulfides from anoxic aqueous solutions (50-200mgS(2-)/dm(3)). The research showed that the form (Na(+) or H(+)) of ionic groups of hybrid materials had a crucial impact on the sulfide removal process. Due to high iron oxide content (35% Fe), advantageous chemical constitution and porous structure, the highest removal efficiency (60mgS(2-)/g) was exhibited by a hybrid polymer obtained using a macroporous carboxylic cation exchanger as the host material. The process of sulfide removal was very complex and proceeded with heterogeneous oxidation, iron(III) oxide reductive dissolution and formation of sulfide oxidation and precipitation products such as iron(II) sulfides, thiosulfates and polysulfides.

A Study on the Condensation Reaction of 4-Amino-3,5-dimethyl-1,2,4-triazole with Benzaldehydes: Structure and Spectroscopic Properties of Some New Stable Hemiaminals

Studies on the stable hemiaminals and Schiff bases formation in the reaction of substituted benzaldehydes with primary 3,5-dimethyl-1,2,4-triazole 4-amine were carried out under neutral conditions. These products were investigated by IR, Raman, MS, 1H- and 13C-NMR spectra as well as by X-ray crystallography. The effect of reaction conditions: temperature, polarity of the solvents utilized, substrate concentration and the ortho and para benzaldehyde substituents on the yield of products was also examined.

Iron(III) bis(pyrazol-1-yl)acetate based decanuclear metallacycles: synthesis, structure, magnetic properties and DFT calculations

The synthesis, structural aspects, magnetic interpretation and theoretical rationalizations for a new member of the ferric wheel family, a decanuclear iron(iii) complex with the formula [Fe10(bdtbpza)10(μ2-OCH3)20] (1), featuring the N,N,O tridentate bis(3,5-di-tert-butylpyrazol-1-yl)acetate ligand, are reported. The influence of the steric effect on both the core geometry and coordination mode is observed. Temperature dependent (2.0-300 K range) magnetic susceptibility studies carried out on complexes 1 established unequivocally antiferromagnetic (AF) interactions between high-spin iron(iii) centers (S = 5/2), leading to a ground state S = 0. The mechanism of AF intramolecular coupling was proved using a broken-symmetry approach within the density functional method at the B3LYP/def2-TZVP(-f)/def2-SVP level of theory.